Make default keyboard handling available in wxVarScrollHelperEvtHandler too.

Factor out the keyboard handling code in wxAnyScrollHelperBase allowing its
reuse in wxVarScrollHelperEvtHandler.

Now wxVarScrollHelperBase handles cursor keys in a sane way by default
too and also allows disabling their handling, just as wxScrolledWindow.

See #15357.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74815 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/vscroll.cpp

@@ -142,6 +142,16 @@ bool wxVarScrollHelperEvtHandler::ProcessEvent(wxEvent& event)
         m_scrollHelper->HandleOnMouseWheel((wxMouseEvent &)event);
     }
 #endif // wxUSE_MOUSEWHEEL
+    else if ( evType == wxEVT_CHAR &&
+                (m_scrollHelper->GetOrientation() == wxVERTICAL) )
+    {
+        m_scrollHelper->HandleOnChar((wxKeyEvent &)event);
+        if ( !event.GetSkipped() )
+        {
+            processed = true;
+            wasSkipped = false;
+        }
+    }
 
     event.Skip(wasSkipped);